Magnetic substrates, composition and method for making the same

ABSTRACT

A process of making a magnetic assembly having at least one magnetic layer and at least one printable substrate layer including the steps of providing a magnetic composition comprising about 70 wt-% to about 95 wt-% of at least one magnetic material and about 5 wt-% to about 30 wt-% of at least one thermoplastic binder, forming the magnetic composition into a magnetic layer, and directly applying the magnetic composition at an elevated temperature in molten form to a printable substrate layer, and to the magnetic composition and any articles made therefrom.

CROSS REFERENCE TO RELATED U.S. APPLICATIONS

This application claims priority from U.S. provisional patentapplication No. 60/253,191 filed Nov. 26, 2000, the content of which isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a method of making a magnetic,printable assembly that will self-adhere to a magnetically attractedsurface, a magnetic composition for making the same, and articles madetherefrom.

BACKGROUND OF THE INVENTION

Flexible permanent magnetic materials are often supplied in the form ofsheets or rolls and have been commercially available for many years.These materials are typically prepared by mixing a powdered ferritematerial with a suitable polymeric or plastic binder into a uniformmixture. The polymeric materials are often elastomers, and the processis therefore typically accomplished through the use of sheet extrusionor calendering. The mixture is converted into strip or sheet form,providing a permanent stable product that is usually somewhat flexible,and that can readily be handled and made into elements of any desiredshape by cutting and/or stamping.

The magnetic material is permanently magnetized so that the resultingelements can act individually as permanent magnets, the magnetic fieldbeing of sufficient strength that they will adhere to a magneticallyattracted surface, such as the surface of an iron or steel sheet, eventhrough a sheet of paper or thin cardboard. Many magnetic materials andthe resultant sheet materials are typically inherently dark in color andit is therefore usual to attach these magnets to a printable substratesuch as paper or plastic by gluing. It is therefore to the paper orplastic that the decorative pattern and/or other information may beprinted. A popular application of such materials is thin, flat magnetshaving on their outer surface a decorative pattern and/or promotionalinformation, including advertisements in direct mailings, newspaperinserts, and so forth, box toppers, coupons, business cards, calendars,greeting cards, postcards, and so forth.

These magnetic pieces may then be placed on a magnetically attractedsurface such as a refrigerator, file cabinet, or other surface wherethey may be used as reminders and are often used to hold sheets of papersuch as notes, recipes, lists, children's artwork, reminders, and so on.

In the usual manufacture of these items, multiple producers are involvedin the process. For example, a printer produces the printed matter onwide web presses or individual sheets. If in web form, the web is cutinto individual sheets and then shipped to a magnet manufacturer wherethe magnetic material and the printed matter are joined through the useof an adhesive layer. Alternatively, the printer may purchase orotherwise obtain magnets and then join the printed matter to the magnetsthrough the use of an adhesive layer, or may have both pieces shipped toa third party where the pieces may be joined through the use of anadhesive layer.

There remains a need in the art to simplify the production process ofsuch magnetic pieces.

SUMMARY OF THE INVENTION

The present invention relates to a unitary process of making a magnetic,printable assembly in which at least one magnetic layer may be directlyformed and joined to a printable layer without the use of an additionaladhesive layer. The adhesion between the magnetic layer and theprintable substrate is sufficient so that no additional adhesive isrequired. The process allows for formation of the magnetic layer andjoining of the magnetic layer to a printable substrate during a singleprocess. The formation and joining are accomplished at an elevatedtemperature sufficient to provide the magnetic layer in pliable orplastic form.

The process may further include a magnetization step which may beaccomplished either when the magnetic layer is at an elevatedtemperature, or when it has cooled to ambient temperatures.

The magnetic layer comprises from about 70 wt-% to about 95 wt-% of atleast one magnetic material and about 5 wt-% to about 30 wt-% of atleast one thermoplastic material.

In one embodiment of the present invention, the magnetic material hasthe general formula M²⁺O6Fe₂O₃ (MFe₁₂O₁₉) where M is a divalent metal.Suitably, M is barium, strontium or lead. In some embodiments, thepolymeric binder includes at least one amorphous polypropylene.

The process involves application of the magnetic layer directly to theprintable substrate at elevated temperatures wherein the magnetic layeris pliable and or in a plastic form. The process has the advantage thatno additional adhesive layer is required.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional side view of the magnetic assembly of thepresent invention.

FIG. 2 illustrates an embodiment of the present invention in which themagnetic layer is found in a discrete location on a printable substratelayer.

FIG. 3 illustrates an embodiment in which the magnetic layer issubstantially equal in length and width to the printable substratelayer.

FIG. 4 a is a perspective view of the magnetic label assembly of thepresent invention shown provided on an article.

FIG. 4 b is an alternative embodiment to that shown in FIG. 4 a in whichthe magnetic assembly is further provided with an overlaminate.

FIG. 5 illustrates an embodiment of the magnetic assembly of the presentinvention in which individual pieces may be produced from a sheet or webmaterial.

FIG. 6 illustrates an alternative embodiment as that shown in FIG. 5 inwhich the magnetic layer is located in discrete areas along the web orsheet of printable substrate.

FIG. 7 is a perspective view of an embodiment of the present inventionin showing a collection of a plurality of individual magneticassemblies.

FIG. 8 illustrates one embodiment of the magnetic assembly of thepresent invention.

FIG. 9 illustrates an alternative embodiment of the magnetic assembly ofthe present invention.

FIG. 10 illustrates another alternative embodiment of the magneticassembly of the present invention.

FIG. 11 is a side view of one embodiment of the magnetic assembly of thepresent invention further including a release liner and an overlaminate.

FIG. 12 is a top down view of the embodiment shown in FIG. 11 in whichthe overlaminate further includes perforations.

FIG. 13 shows the embodiment described in FIGS. 11 and 12 in sheet form.

FIG. 14 is a side view of an alternative embodiment of the magneticassembly of the present invention.

FIG. 15 is a top down view of the embodiment shown in FIG. 14.

DETAILED DESCRIPTIONS OF THE PREFERRED EMBODIMENTS

The following description is intended for illustrative purposes only,and is not intended as a limit on the scope of the present invention.One of skill in the art will recognize various alternative embodimentsand variations of the embodiments which also may be employed herein.

The present invention relates to a novel method of making a printable,magnetic assembly, and to a magnetic composition and articles madetherefrom.

The magnetic substrate layer may suitably include about 75 weight % toabout 95 weight %, more suitably about 80 weight % to about 92 weight %,and most suitably about 85 wt-% to about 90 wt-% of a magnetic material,suitably about 5 wt-% to about 25 wt-%, more suitably about 8 wt-% toabout 20 wt-% and most suitably about 10 wt-% to about 15 wt-% of apolymeric binder. The magnetic material is uniformly dispersed in thepolymeric binder.

As used herein, the term “magnetic” (when applied to a substrate,article, object, etc.) shall refer to any material which exhibits apermanent magnetic behavior or is readily permanently magnetized.

Magnetic materials which are particularly suitable for use hereininclude the ferrites having the general formula (M²⁺O6Fe₂O₃) MFe₁₂O₁₉where M represents Ba or Sr.

Other examples of magnetic materials suitable for use herein include arare earth-cobalt magnet of RCO₅ where R is one or more of the rareearth elements such as Sm or Pr, yttrium (Y), lanthanum (La), cerium(Ce), and so forth.

Other specific examples of magnetic materials include, for instance,manganese-bismuth, manganese-aluminum, and so forth.

The method of the present invention is not limited to any particularmagnetic material, and the scope of the invention is therefore notintended to be limited as such. While the above described materials findparticular utility in the process of the present invention, othermaterials which are readily permanently magnetized may also find utilityherein.

The magnetic composition suitably includes about 70 wt-% or more of themagnetic material as to have a sufficient attractive force for practicaluses. However, it is usually impractical to employ more than 95 wt-% ofthe magnetic material because of production concerns, and also becauseof the difficulty of retaining more than this in the binder material.Furthermore, including more than about 95 wt-% of the magnetic materialmay lead to a rougher surface. The magnetic material is often suppliedin a powder form.

The magnetic strength of the finished product is a function of theamount of magnetic material or powder in the mix, the surface area,thickness, and method of magnetization (e.g. whether it is aligned ornot).

The thermoplastic material, often referred to in the industry as athermoplastic binder, suitable for use in the process of the presentinvention may include any polymeric material that is readily processablewith the magnetic material on, for instance, the thermoplastic or hotmelt processing equipment as described in detail below. Suchthermoplastic materials include both thermoplastic elastomers andnon-elastomers or any mixture thereof.

The thermoplastic composition may be selected based on, for one, thetype of printable substrate which is being used, and the adhesionobtained between the thermoplastic composition and the printablesubstrate.

Examples of thermoplastic elastomers suitable for use herein include,but are not limited to, natural and synthetic rubbers and rubbery blockcopolymers, such as butyl rubber, neoprene, ethylene-propylenecopolymers (EPM), ethylene-propylene-diene polymers (EPDM),polyisobutylene, polybutadiene, polyisoprene, styrene-butadiene (SBR),styrene-butadiene-styrene (SBS), styrene-ethylene-butylene-styrene(SEBS), styrene-isoprene-styrene (SIS), styrene-isoprene (SI),styrene-ethylene/propylene (SEP), polyester elastomers, polyurethaneelastomers, to mention only a few, and so forth and mixtures thereof.Where appropriate, included within the scope of this invention are anycopolymers of the above described materials.

Examples of suitable commercially available thermoplastic elastomerssuch as SBS, SEBS, or SIS copolymers include KRATON® G (SEBS or SEP) andKRATON® D (SIS or SBS) block copolymers available from Kraton Polymers;VECTOR® (SIS or SBS) block copolymers available from Dexco Chemical Co.;and FINAPRENE® (SIS or SBS) block copolymers available from Atofina.

Some examples of non-elastomeric polymers include, but are not limitedto, polyolefins including polyethylene, polypropylene, polybutylene andcopolymers and terpolymers thereof such as ethylene vinyl acetatecopolymers (EVA), ethylene n-butyl acrylates (EnBA), ethylene methyl(meth) acrylates including ethylene methyl acrylates (EMA), ethyleneethyl (meth) acrylates including ethylene ethyl acrylates (EEA),interpolymers of ethylene with at least one C₃ to C₂₀ alphaolefin,polyamides, polyesters, polyurethanes, to mention only a few, and soforth, and mixtures thereof. Where appropriate, copolymers of the abovedescribed materials also find utility herein.

Examples of polymers useful herein may be found in U.S. Pat. No.6,262,174 incorporated by reference herein in its entirety. Polymericcompositions exhibiting high hot tack have been found to be particularlysuitable for use herein. Hot tack is a term of art known to those ofordinary skill.

Examples of commercially available non-elastomeric polymers include EnBAcopolymers available from such companies as Atofina under the tradenameof LOTRYL®, from ExxonMobil under the tradename of ESCORENE®, from DuPont de Nemours & Co. under the tradename of ELVALOY®; EMA copolymersavailable from Exxon Chemical Co. under the tradename of OPTEMA®; EVAcopolymers are available from Du Pont under the tradename of ELVAX® andfrom Equistar under the tradename of ULTRATHENE® to name only a few.

In some embodiments of the present invention, the binder includes atleast one polyolefin or polyalphaolefin, or a copolymer or terpolymerthereof. Examples of useful polyolefins include, but are not limited to,amorphous (i.e. atactic) polyalphaolefins (APAO) including amorphouspropylene homopolymers, propylene/ethylene copolymers,propylene/butylene copolymers and propylene/ethylene/butyleneterpolymers; isotactic polyalphaolefins; and linear or substantiallylinear interpolymers of ethylene and at least one alpha-olefinincluding, for instance, ethylene and 1-octene, ethylene and 1-butene,ethylene and 1-hexene, ethylene and 1-pentene, ethylene and 1-heptene,and ethylene and 4-methyl-1-pentene and so forth. In some embodiments,it may be preferable to employ a small amount of another polymer incombination with the polyalphaolefin such as maleic anhydride graftedpolymers which have been used to improve wetting and adhesion. Otherchemical grafting can be used, but maleic anhydride is by far the mostcommon. Usually only a few percent in grafting (1-5%) are used and mosttend to be ethylene or propylene copolymers.

The terms “polyolefin” and “polyalphaolefin” are often usedinterchangeably, and in fact, are often used interchangeably to describeamorphous polypropylenes (homo-, co- and terpolymers). For a detaileddescription of such materials, see U.S. Pat. No. 5,482,982, U.S. Pat.No. 5,478,891 and U.S. Pat. Nos. 5,397,843, 4,857,594, each of which isincorporated by reference herein in its entirety.

The term “alpha” is used to denote the position of a substituting atomor group in an organic compound.

As used herein, the terms “copolymer” and “interpolymer” shall be usedto refer to polymers having two or more different comonomers, e.g.copolymer, terpolymer, and so forth.

Examples of commercially available amorphous polyolefins suitable foruse herein include those available under the tradename of REXTAC® fromHuntsman Polymers including polypropylene homopolymers,propylene/ethylene copolymers and propylene-butene copolymers;VESTOPLAST® APAOs available from Hüls including homopolymers andcopolymers, as well as terpolymers of propylene/ethylene/butene; as wellas those available from Rexene and those available under the tradenameof EASTOFLEX® available from Eastman Chemical Co. in Kingsport, Tenn.

Examples of copolymers of a polyolefin and at least one alpha-olefininclude metallocene catalyzed polyolefins (interpolymers of ethylene andat least one alphaolefin) commercially available from Exxon under thetradename EXXACT®, and from DupontDow Elastomers under the tradenameENGAGE®, and from Dow under the tradename AFFINITY®.

In one particular embodiment, the binder is an amorphous polyalphaolefinavailable from Eastman Chemical Co. under the tradename of EASTOFLEX®.Amorphous polyalphaolefins when used in combination with the magneticmaterial have been found to provide excellent adhesion to the printablesubstrate without the need for further formulation. However, somepolymeric materials may require the addition of tackifying resins,plasticizers, and so forth to provide adequate adhesion. The addition oflow molecular weight plasticizers and/or tackifying resins can alsoimprove the processability of the composition as well by changingrheological properties and/or lowering the melt viscosity of thecomposition.

Any of the polymeric materials useful herein may be used in combinationwith one another. Furthermore, other polymeric materials notspecifically described herein also find utility in the presentinvention. The list described above is intended for illustrativepurposes only, and is not intended to limit the scope of the presentinvention. One of skill in the art would understand that there are vastnumbers of polymeric materials available that may find utility herein.

Tackifying resins are available from numerous sources including many ofthe companies described above, and include, for instance, hydrocarbontackifying resins such as those available from Eastman Chemical Co.under the tradename of EASTOTAC®; ESCOREZ® petroleum hydrocarbon resinsavailable from ExxonMobil; PICCOTAC® and PICCOLYTE® polyterpene resinsavailable from Hercules; FORAL® hydrogenated rosins and rosin esterresins available from Hercules; WINGTAC® petroleum hydrocarbon resinsavailable from Goodyear; REGALREZ® hydrocarbon resins and REGALITE®hydrogenated aromatic resins available from Hercules Inc.; and so on andso forth.

Plasticizers are available from many sources and include plasticizingoils, for instance. Plasticizing oils are often petroleum based and areavailable from various petroleum companies.

Waxes may also be optionally added to the compositions to lower the meltviscosity and/or change rheological characteristics.

Other optional ingredients include, but are not limited to,antioxidants, dyes or pigments, UV agents, and so forth. Such optionalingredients are known to those of skill in the art and are typicallyadded in low concentrations which do not adversely affect the physicalcharacteristics of the composition.

The list of materials described above is intended for illustrativepurposes only, and is by no means exclusive of the materials which maybe employed in the magnetic composition herein, and as such is notintended as a limit on the scope of the invention herein.

The amount of adhesion required between the printable substrate and themagnetic composition will vary depending on application, and on theprintable substrate employed. It may be desirable that the magneticcomposition have sufficient adhesion to remove fiber from the printablesubstrate if it is, for instance, paper. Lack of fiber transfer may notalways be indicative of poor adhesion however. For instance, a lack ofdelamination may be adequate as well. For other types of substrates suchas fabrics, plastics or metallic substrates it may be desirable that themagnetic layer and printable substrate layer do not pull apart easily,or do not delaminate.

Bond strength between the magnetic layer and the printable substrate maybe tested using 180° or 90° peels for instance, as is known in the art.Such methods may be found under the ASTM testing methods. The amount offorce required to peel the substrates apart will vary depending on theend use and the printable substrate. For some applications a peel forceof about 200 to 400 g/inch is adequate and 400 to 450 g/inch an upperlimit, while for some, the peel strengths may be upwards of 1000 to 1500g/inch or more. For instance, for thermosetting polymeric compositions,peel strengths are up to 1000 or 1500 g/inch or higher.

It is desirable that the resultant magnetic composition have little orno surface tack under ambient temperatures. The binder and mixture arevery shear rate sensitive exhibiting Bingham plastic flow. In hot meltapplication, viscosity can be as low as 4000 cps at 300° F. (about 150°C.) or as high as 200,000 cps at 300° F. (about 150° C.). Becausetemperature is a significant factor, it is not uncommon for extrusioncoating to occur at temperatures of as high as about 600° F. to about650° F. (about 315° C. to about 345° C.) melt temperatures.

The temperature at which the magnetic composition is applied to thesubstrate may be quite different from the temperature inside theextruder. The magnetic composition after exiting the extruder and theapplication head, and thus after formation, i.e. shaping, of themagnetic layer, may have cooled to a substantial degree at the time ofapplication of the now formed magnetic layer to the printable substratelayer. However, the magnetic composition should remain at an elevatedtemperature high enough to achieve an adequate bond between the magneticlayer and the printable substrate layer.

The magnetic material and the thermoplastic binder and/or otheringredients are blended at elevated temperatures using standardthermoplastic mixing equipment such as extruders, Baker Perkins, Banburymixers, single or twin screw extruders, Farrell Continuous mixers, andhigh shear mixing equipment.

The mixture may be compounded and made into a form, such as slats,pellets or any form known in the art suitable for feedstock forextrusion or other melt processing equipment, which is then delivered tothe coating company. The coating company may then use a high pressuresingle screw extruder, or other processing equipment to melt andpressurize the mixture, to force it through an application head such asa slot die, rotary screen head, or other such application head, at thecoating station. Thus, the extruder or other hot melt equipment suppliesthe resultant magnetic composition directly to the application head.During extrusion or other melt processing of the magnetic composition,the temperature may be high enough that the composition is considered tobe molten, i.e. in melted or liquid form.

In an alternative embodiment of the present invention, variousingredients may be supplied to the extruder in individual pellets,slats, and so forth. For instance, if more than one thermoplastic bindermaterial is employed, they do not have to be supplied as a mixturealready in pellet or slat form. They may each be supplied in pellet orslat form individually, for example.

Coating companies can use a variety of application processes known inthe art. Examples of application processes useful in applying themagnetic composition to the printable substrate include, but are notlimited to, slot die coating, roll coating or reverse roll coating,knife-over-roll gravure and reverse direct gravure, wire rod coating,air-knife coating, slot-orifice coating, screen printing with a hotscreen, and so forth.

In one embodiment of the present invention, slot die coating is used incombination with a single screw extruder.

In another embodiment of the present invention, a method referred to inthe industry as flex-o-press is employed. The term “flex-o-press” asused herein, generally refers to a four roll coating method by which afirst roll which is heated, and typically turns at a speed which is halfof the second roll. The second roll carries the thermoplastic/magneticmixture. A third roll is a roll-plate roll which is a siliconerubberized roll and may have a patterned surface with raised areas forapplication of the magnetic composition of the present invention to theprintable substrate in a predetermined pattern. This roll comes intolight contact with the second roll and then transfers thethermoplastic/magnetic mixture to a fourth roll. See Roll Coating by RT. Schorenberg, Modern Plastic Encyclopedia, 1984-1985, pp. 202-203,which is incorporated herein by reference in its entirety. Anotheruseful reference is Coatings Technology Handbook, 2nd Edition, Satas andTracton, Marcel Dekker, Inc., 2001 also which is incorporated byreference herein in its entirety. Desirably, the processing equipmentincludes a chill roll for increasing the speed with which the resultantmagnetic composition, including at least the magnetic material and athermoplastic binder, cools and sets. This is advantageous for morerapidly processing the resultant composition into rolls or sheets, forinstance.

Line speeds may vary anywhere up to 500 feet per minute or higher.Previous methods, in contrast, allowed line speeds of only about 40-80feet per minute. The present invention thus allows line speeds that aremuch faster than currently used methods. The line speed may be limitedby the capacity of the extruder or other application equipment employedin the present method, as well as by the type and size of the die,nozzle, or other application head employed, the pressure used, theviscosity of the magnetic composition, and the temperature ofapplication as is known to those of ordinary skill in the art.

Any method which allows the direct application of the thermoplastic,magnetic composition at an elevated temperature when it is in a pliableor when it is in its plastic form to the printable substrate may beemployed herein. Using the method of the present invention, the magneticthermoplastic composition is directly adhered to the desired substratein any desired shape or form without the need for an additional adhesivelayer. Thus, the resultant magnetic layer is both formed and joined tothe printable substrate layer in a unitary or single process.

Previous methods, in contrast, require the formation of the magneticlayer, the cutting of the magnetic layer, and then bonding the magneticlayer to the substrate through the use of an additional adhesive layerto form the magnetic assembly which is thus done using multipleprocesses. The magnetic layer is supplied either in roll form, or inpre-cut form in their desired shapes as required by the purposes forwhich the magnetic layer is to serve and then bonded to the printablesubstrate layer. The present invention, in contrast, allows theformation of the entire magnetic assembly in one process. Thus, thepresent invention provides a more efficient process over previousmethods.

Using the method of the present invention, the mixture of binder andmagnetic material is applied to a printable substrate at an elevatedtemperature wherein the thermoplastic binder is in a pliable or plasticform. The present invention forms the magnetic composition into itsfinal form at a temperature sufficient to provide adequate wetting andadhesion between the magnetic composition and the printable substrate.Of course, the adhesion will also depend on the binder compositionselected. Some binders will provide better adhesion than others.

The substrate to which the magnetic composition may be joined using theprocess of the present invention may be any suitable printablesubstrate, including, for example, paper and paper products, pasteboard,plastic or polymeric materials, metal, release liners such as siliconerelease liner, textiles or fabrics, and so forth. Combinations of any ofthe substrates may also be employed. In some embodiments, a releaseliner may be employed in combination with another printable substrate,one on each side of the magnetic layer, for instance. The magneticassembly which includes the printable substrate and the magnetic layermay then be removed from the release liner at the point of use.

The application temperature required may depend on numerous factorsincluding the melting temperature of the thermoplastic binder, theviscosity of the resultant magnetic composition, and so forth. Themelting temperature and viscosity may vary depending not only on thetype of binder used, but on the various other ingredients which may beemployed in the magnetic composition as described above. The higher theviscosity or melting temperature, the higher the temperature that may berequired to successfully apply the magnetic composition. This of coursealso depends on the application equipment being employed. In general,thermoplastic materials are applied at temperatures of about 275° F. toabout 375° F. (about 135° C. to about 190° C.), although some may beapplied at higher or lower temperatures. For instance, very lowviscosity thermoplastics may be applied at temperatures of as low asabout 190° F. (about 90° C.). Some may be applied at temperatures ashigh as about 400° F. (about 205° C.), or higher, for instance polyamidematerials are often applied at temperatures of about 400° F.Temperatures used, can even exceed 650° F., however. However, for mostthermoplastic materials higher temperatures lead to more rapiddegradation of the material. An often used application temperature rangeis about 325° F. to about 375° F. (about 160° C. to about 190° C.), with350° F. (about 175° C.) being very common. In one embodiment of thepresent invention, polypropylene is used and may be applied attemperatures of over 400° F. (205° C.). Yet, using extrusion techniquespolyethylene is commonly extruded at above 600° F. (306° C.) at highspeeds.

The temperature should be sufficient to lower the viscosity of thethermoplastic material to allow the thermoplastic material tosufficiently adhere to the printable substrate. This may involvepenetration into, or “wet out” of the substrate surface to which it isbeing applied. The thermoplastic material must be sufficiently adheredto the substrate so that delamination from the substrates does notoccur.

Using the method of the present invention, the resultant magneticcomposition may be advantageously applied in a thin layer of about 0.002inches to about 0.030 inches (about 50μ to about 765μ; about 2 mils toabout 30 mils), suitably about 0.002 inches to about 0.020 inches (about50μ to about 510 μl; about 2 mils to about 20 mils) and most suitablyabout 0.002 inches to about 0.012 inches (about 50μ to about 305μ; about2 mils to about 12 mils) thick. The present invention allows forapplication of a thinner layer of the binder/magnetic mixture. Previousextrusion and calendering methods, in contrast, did not allow formagnetic layers of less than about 4 mils to about 8 mils, and oftenmore than 10 mils.

In one embodiment of the present invention, a ribbon of the magneticcomposition is applied at an elevated temperature in a plastic state toa printable substrate. The ribbon may be applied to the substrate sothat it is dimensionally coextensive with the printable substrate, i.e.the same length and width, or it may be applied to the substrate indiscrete, preselected areas only. Furthermore, several ribbons may beapplied to the substrate simultaneously, and they may be appliedintermittently in a discontinuous pattern. The application line may beequipped such that pressure is applied to the ribbon(s) to press theribbon(s) into the printable substrate. For instance, a chill roll maybe employed for this purpose.

The surface of the ribbon may also be contacted by a magnetizing rollwhich smooths, cools and magnetizes the ribbon(s). When this is donewhile the ribbon is still fluid, it provides an enhanced magnetic effectknown as alignment. The ribbon may be applied at a thickness of betweenabout 0.002 inches and to about 0.020 inches (about 50μ to about 510μ).

In broad terms, the method of the present invention allows the magneticcomposition to be formed and applied directly to the printable substratein a single, unitary process. The width, thickness and length of themagnetic layer may be individually tailored to any desired size, and maybe designed to cover all of the printable substrate being thereforeapplied generally dimensionally coextensive with the printablesubstrate, or may be applied to cover only some discrete portion of thesubstrate. Furthermore, it may be applied in a patterned form such as byusing the silicone rubberized roll as described above (e.g. flexopress).

Furthermore, the magnetic composition may be formed and affixed to theprintable substrate in a finished form substantially simultaneously. Thethickness and width, or the thickness, width and length may be in theirfinal fixed form. As used herein, the term “substantiallysimultaneously” may be used to indicate that it is occurring during asingle process of manufacture.

The magnetic composition may be fully magnetized during themanufacturing process by providing a magnetic field on the line theentire width of the web after application of the magnetic composition tothe printable substrate. The magnetization step may be optionallyincluded after printing, or after formation of the article to itsdesirable size and shape by cutting, stamping or punching as describedbelow.

In addition, the magnetizing step may be carried out while thethermoplastic binder is at an elevated temperature. This results in analignment of the magnetic particles with a significant increase in themagnetic strength of the article as compared to the same articlemagnetized at ambient temperature. See Sawa 4022701 and Ito 6190513.

Optionally, indicia, i.e. printed matter, may be applied to theprintable substrate prior to joining with the magnetic layer, or it maybe printed after it has been joined with the magnetic layer. For ease ofproduction, it may be desirable to print after the magnetic material hasbeen joined to the printable substrate. However, no print need beapplied to the printable substrate. For instance, in the case ofmagnetic note pads, no print may be applied. This allows the end user toapply their own notes and reminders to individual sheets of paper.

Once printed matter has been applied to the printable substrate,lacquers, films or other protective surfaces which also improve theappearance of the now printed substrate, may be provided on the surfaceof the printed substrate. These or similar materials may also be appliedto the exposed surface of the magnetized layer to prevent unintendedsticking or “blocking” of the combined article to itself or othersubstrates if necessary.

Once the entire magnetic assembly has been produced in roll or sheetform, the desired shapes may be cut, punched, stamped, or so forth fromthe assembly, either at the point of manufacture of the magneticmaterial, or by those to which the magnetic assembly is supplied asdesired. Laser cutting is one example of a method by which variousarticles may be formed from the sheet or web.

FIG. 1 illustrates generally at 10, a magnetic assembly as producedusing the process of the present invention. Magnetic layer 12 is joinedto a printable substrate layer 14 without the use of an additionaladhesive layer.

FIG. 2 illustrates generally at 10, one embodiment of the presentinvention in which the magnetic layer 14 is applied in a discrete areaof the printable substrate 12.

FIG. 3 shows generally at 10, an alternative embodiment of the magneticassembly of the present invention in which the magnetic layer 14 isshown substantially coextensive with the printable substrate layer 12both in length 16 and width 18.

In one particular embodiment of the present invention, the magneticassembly is a magnetic label assembly. The magnetic label assembly is amagnetic label assembly which includes the magnetic layer 14 and theprintable substrate layer 12 having the desirable indicia or informationprinted thereon.

FIG. 4 a illustrates generally at 10 a magnetic label assembly of thepresent invention with the printable substrate layer 12 joined to amagnetic layer 14. The magnetic layer is further attached to a releaseliner 26. Release liners include those substrates which includesilicones, among others. This may be accomplished using any means knownin the art such as through the use of a removable pressure sensitiveadhesive, such as a removable hot melt adhesive, or dry releaseadhesive, although in some embodiments, no adhesive may be required.Furthermore, the entire assembly of printable substrate layer 12,magnetic layer 14 and release liner 26 may be further adhered to anarticle such as a package, cup, book, magazine or other such article 22through the use of a pressure sensitive or dry release adhesive (notshown). The magnetic assembly 10 may then be used in commerce foradvertising or promotional purposes.

In one particular embodiment, the magnetic assembly is a magnetic labelassembly. The magnetic label assembly is releasably adhered by anyadhesive known to those of skill in the art including water basedadhesives and hot melt adhesives, as well as others to the base article.Suitably, the adhesive is a pressure sensitive adhesive, and even moresuitably, a removable pressure sensitive adhesive, although the pressuresensitive adhesives employed may also be of the permanent orsemi-permanent type as well. Release liners are by their naturedifficult to adhere so the type of adhesive employed is not limited.Therefore, depending on the release liner employed, semi-permanent andpermanent adhesives may also be employed, as well as non-pressuresensitive adhesive. The selection of adhesives is known to those ofskill in the art. However, in any event, it is desirable that theadhesive form a stronger bond with the base article, than with therelease liner to allow easy removal of the magnetic assembly from thebase article. Once the magnetic assembly is removed, it may then beplaced on a magnetic surface such as a refrigerator, cabinet, magneticbulletin board or notice board, and so forth for the purposes ofdisplaying the printed indicia thereon.

One example of an adhesive suitable for use herein includes anethylene-vinyl acetate copolymer latex, and even more specifically, anaqueous dispersion containing 60% solids by weight including 22.4 wt-%ethylene and 77.6 wt-% vinyl acetate. The adhesive may optionallyinclude a crosslinking agent and/or an inorganic peroxide among otheroptional ingredients known to those of skill in the art.

The base article may be formed from any desired material and can haveany structure to which the magnetic label assembly may be releasablyadhered. In the above example, the adhesive is therefore between therelease liner and the base article.

FIG. 4 b shows an alternative embodiment in which the printablesubstrate layer 12 further has an overlaminate 30 which extends over theprintable substrate layer 12 which is dimensionally substantiallyequivalent in at least length and width to the magnetic layer (notshown). The overlaminate is preferably a clear polymeric film material.In this embodiment, no adhesive is required between the magnetic layerand the release liner or the release liner and the article 22. Theoverlaminate has perforations which are substantially dimensionallyequivalent in length and width to the printable substrate layer 12 andthe magnetic layer (not shown) for easy removal of the magnetic assemblywhich includes the printable substrate layer and the magnetic layer. Anynumber of perforations may be employed. Desirably, at least twoperforations on opposing sides of the assembly are desirable.Embodiments such as these are further discussed in relation to FIGS.11-13 described in detail below.

Optionally, the overlaminate may have substantially the same length, buta slightly larger width, or in the alternative, the substantially samewidth, but a different length. All sides of the overlaminate, or twoopposing sides of the overlaminate can be secured to a base articlethrough the use of an adhesive, for example. The adhesive may be appliedin thin strips, dots, or other patterns known to those of skill in theart. The adhesive may be either removable, permanent or semi-permanentas well as pressure sensitive or non-pressure sensitive. Suitably, theadhesive is a permanent adhesive. The type of adhesive selected,however, is strictly a preference based on the user. The mainconsideration is that the magnetic assembly be removable from theoverlaminate as well as from the base article. This may be done, forexample, through the use of perforations, wherein part of theoverlaminate remains with the base article, and part remains with themagnetic assembly. If perforations are employed, it may be desirable toplace the perforations just inside of the adhesive.

The magnetic assembly may then be removed from the base article bybreaking the perforations. In the particular embodiment described abovein which an overlaminate is employed, the magnetic assembly may beremovably adhered to the release liner through the use of an adhesive,but no adhesive is required because the overlaminate secures themagnetic assembly to the base article. Once removed, the magneticassembly may be self-adhered to a magnetic surface such as arefrigerator, cabinet, magnetic bulletin or notice board, and so forth.

An optional embodiment may have the magnetic assembly 10 packaged in athin film for instance, such as a polyolefin or polyolefin copolymerbased film, saran, mylar, or some such film. An application similar tothis is referred to in the bookbinding industry or pressure sensitiveadhesive industry as magazine tipping wherein advertisements or samplesare temporarily adhered to a magazine or book. Once removed from thepackage, book, magazine or so forth, the magnetic assembly 10 may beself adhered to a magnetic surface such as a refrigerator or filingcabinet, for instance.

FIG. 5 illustrates generally at 15 a magnetic assembly of the presentinvention prior to forming the individual pieces from the sheet or webin which the magnetic layer 14 is shown substantially coextensive inlength 16 and width 18 with the printable substrate layer 12. In thisembodiment, individual pieces such as labels, business cards, and soforth, for example, have been printed on printable substrate layer 12(print not shown) in a sheet form. The individual magnetic pieces 24 maythen be later cut, stamped, punched and so forth out of the sheet at theperforations 26 forming individual magnetic pieces 24.

FIG. 6 illustrates an alternative embodiment of that shown in FIG. 5 inwhich the magnetic layer 14 has been applied in ribbons and pressed indiscrete areas only on the printable substrate layer 12. In thisembodiment, a strip of magnetic layer 14 is shown at the top of whatwill be each individual piece 24 when cut at the perforations 26.

Optionally, the individual pieces may be bound together in a processsimilar to what is referred to in the industry as “perfect” binding.Using this process, the individual pieces or sheets of printablesubstrate having the magnetic layer are stacked in a block or arrangedin a pad format, held in a clamp to form a block, and then boundtogether using an adhesive. The adhesive is applied to one side of thestack or pad, which also may be referred to as the “backbone” of theblock. A cover may be adhered to the backbone to prevent the adhesivefrom adhering in the case of a pressure sensitive adhesive. If anon-pressure sensitive adhesive is employed, and it is not tacky, thenno cover may be necessary. The adhesive may be applied by spraying,rolling or any other means known in the art. An alternative to employingan adhesive is to stack the individual magnetic pieces in a stack, blockor pad, and then shrink wrapping them together. FIG. 7 illustratesgenerally at 20, a stack or block of individual magnetic assemblies 10.FIGS. 8, 9 and 10 illustrate various embodiments in which magnetic layer14 is applied to the printable substrate 12, in this embodiment, blankpaper. Of course, the paper can be personalized, or have messagesprinted on it, and so forth.

FIG. 11 illustrates generally at 50 a cross-sectional view of analternative embodiment of the magnetic assembly produced according tothe present invention. Magnetic layer 14 is joined to printablesubstrate layer 12 without the use of an additional adhesive layer.Magnetic layer 14 a release liner 26 is employed in combination with andnext to the magnetic layer 14. In this instance, an overlaminate 28 isemployed to hold the assembly together. Overlaminate 28 has perforations30 which may be employed to remove the magnetic assembly 10 whichincludes the printable substrate layer 12 and the magnetic layer 14,from the release liner 26. In this case, no adhesive is employed to holdthe release liner 26 to the magnetic layer 14. FIG. 12 illustrates a topdown view showing the perforations 30 in the overlaminate 28. These canbe produced in sheet form, for instance, as shown generally at 60 inFIG. 13.

In one particular embodiment, the magnetic assembly as described aboveis a magnetic label assembly.

The assembly as shown in FIGS. 11-13 is a four layer structure as showncross-sectionally in FIG. 11. No adhesives are employed in thisembodiment. The entire assembly includes a release liner 26, a magneticlayer 14, a printable substrate layer 12 and a clear over laminate 28.

FIG. 14 illustrates an alternative embodiment in which the magneticlayer 14 being applied in discreet individually sized pieces 15. Thisassembly is of a two-layer construction having only the printablesubstrate layer 12 and the magnetic layer 14. The printable substratelayer 12 has perforations 30 which coincide with each individualdiscreet magnetic piece 15 and allow each individual magnetic assembly10 of the present invention which includes the printable substrate layer12 and the magnetic layer 14 to be easily removed from the sheet 60. Themagnetic pieces 15 are directly adhered to the printable substrate layer12. FIG. 15 illustrates a top down view of the embodiment of themagnetic sheet described in FIG. 14 showing perforations 30 in theprintable substrate layer 12 which coincide with the individual magneticpiece 15 so as to provide easy removal.

The above described figures illustrate only some of the embodiments ofthe present invention and are intended for exemplary purposes only, anddo not limit the scope of the present invention to those embodiments asdescribed herein.

The method of the present invention wherein the magnetic composition isapplied directly to the printable substrate, allows for all of the othersteps to also be included in the unitary manufacturing process of thepresent invention. Optionally any combination of the steps of printing,coating and formation of the article by cutting, stamping, punching, andso forth, may be included in the unitary process.

Articles which may be produced in this way, include, but are not limitedto, promotional pieces, greeting cards, postcards, businessadvertisements, magnetic business cards, appointment reminder cards,announcements, advertisements, coupons, labels, calendars, schedules,tourist attractions, picture frames, other informational purposes, andso forth which have a magnetic surface joined to a printable surfacewhich may be self-adhered or self-sticking to a metallic surface fordisplay.

Announcement cards may include, for instance, baby announcements,showers, weddings, anniversaries, parties, “we've moved” announcements,and so forth.

Promotional products include, for example, restaurant advertisements,auto services, veterinary clinics, real estate agents, lawn careservices, insurance agents, and so on and so forth. These promotionalpieces may conveniently include phone numbers and addresses.Furthermore, adding calendars to such pieces may improve the chances foruse on refrigerators, for instance.

Other examples include, schedules such as schedules for athletic-events,school events, and so forth. Such articles are intended for exemplarypurposes only, and are not intended to limit the scope of the presentinvention. There are numerous uses for the magnetic assembly of thepresent invention, and one of ordinary skill in the art would 110 knowhow to use the magnetic assembly or modifications thereof, for furtherarticles not described herein.

The items described above may be distributed through direct mailings,through addition to magazines or newspapers, and so forth.

Alternatively, the magnetic assembly of the present invention may beemployed in children's toys such as magnetic paper dolls or characterfigures, or for example, letters or numbers of self-adhering to magneticbulletin boards.

The above disclosure is intended to be illustrative and not exhaustive.This description will suggest many variations and alternatives to one ofordinary skill in this art. All these alternatives and variations areintended to be included within the scope of the claims where the term“comprising” means “including, but not limited to”. Those familiar withthe art may recognize other equivalents to the specific embodimentsdescribed herein which equivalents are also intended to be encompassedby the claims.

Further, the particular features presented in the dependent claims canbe combined with each other in other manners within the scope of theinvention such that the invention should be recognized as alsospecifically directed to other embodiments having any other possiblecombination of the features of the dependent claims. For instance, forpurposes of claim publication, any dependent claim which follows shouldbe taken as alternatively written in a multiple dependent form from allprior claims which possess all antecedents referenced in such dependentclaim if such multiple dependent format is an accepted format within thejurisdiction (e.g. each claim depending directly from claim 1 should bealternatively taken as depending from all previous claims). Injurisdictions where multiple dependent claim formats are restricted, thefollowing dependent claims should each be also taken as alternativelywritten in each singly dependent claim format which creates a dependencyfrom a prior antecedent-possessing claim other than the specific claimlisted in such dependent claim below. For example, claim 3 mayalternatively taken as depending from claim 2 as well as claim 1; claim4 may be alternatively taken as depending from any of claims 2-3; claim5 may be taken as alternatively depending from any of claims 1-3; claim6 may be alternatively taken as depending from any of claims 1-4; etc.

Those skilled in the art may recognize other equivalents to the specificembodiments described herein which equivalents are intended to beencompassed by the claims attached hereto.

The following non-limiting examples are further illustrative of thepresent invention.

EXAMPLES Example 1

Amorphous polypropylene P #1023 supplied by the Eastman Chemical Co. wasmixed with HM 410 Starbond ferrite powder supplied by Hoosier Magneticsin amounts of 85 wt-% polypropylene and 15 wt-% of the ferrite powder.The resultant mixture was processed at a temperature of between about325° F. and 375° F. (about 165° C. to about 190° C.) and formed intoribbons using an extruder/slot die head on a printable paper substrate.The thickness of the mixture was varied between about 0.003 and 0.012inches (μ to μ).

This test was run at speeds varying between 250-500 feet per minute forcoating discrete ribbons, and about 80 feet per minute for fullcoverage.

1-60. (canceled)
 61. A process of forming a magnetic assembly having atleast one magnetic layer having dimensions of thickness, width andlength, and at least one printable substrate layer having dimensions ofthickness, width and length, comprising the steps of: a) providing amagnetic hot melt composition at a temperature between about 135° C. andabout 205° C. with an extruder which is a single screw or double screwextruder, the magnetic hot melt composition comprising about 80 wt-% toabout 95 wt-% of at least one magnetic material and about 5 wt-% toabout 20 wt-% of at least one thermoplastic binder selected fromcopolymers of ethylene and vinyl acetate and mixtures thereof; b)directly applying said magnetic hot melt composition with a slot diehead at an elevated temperature when it is pliable to a printablesubstrate layer, the printable substrate layer formed of paper.
 62. Themethod of claim 61 wherein said magnetic hot melt composition isprovided with a single screw extruder.
 63. The method of claim 61wherein said magnetic hot melt composition is applied at a temperaturebetween about 135° C. and about 190° C.
 64. The method of claim 61wherein said magnetic hot melt composition comprises about 85 wt-% toabout 95 wt-% of said at least one magnetic material and about 5 wt-% toabout 15 wt-% of said at least one thermoplastic binder selected fromcopolymers of ethylene and vinyl acetate and mixtures thereof.